I just ran into the same issue. The objectives I’ve completed are:
Brief your squad on the mission
Board the ark
Get to the ark’s hold
Place the ghostfire charges in the hold
After placing the charges, the objective for placing them shows it’s completed, but then, nothing…
Ok, finally got it to work. I ran it one more time, but this time, I just hung out in the hold for about 2 minutes after placing the charges. Maeva started talking again and the mission then ran as intended.